1. Field of the Invention
The present invention relates to a manual ventilation bag and to a breathing apparatus employing a manual ventilation bag.
2. Description of the Prior Art
Manual ventilation bags are customarily used by a physician for controlling or supporting a patient""s breathing. The physician squeezes the bag to press gas toward the patient and releases the bag to permit an exhalation. There are two basic forms of bags, having very different characteristics. One is the hard bag, which is made to re-inflate itself whenever squeezed. The other is the soft bag, which adapts to the flows and pressures within the system and provided by the operator. The present invention relates to ventilation bags of the soft kind.
When the physician operates the soft manual ventilation bag, he or she is able to feel the patient""s lungs (resistance and compliance). This is an outstanding advantage in comparison to the hard bags. One disadvantage of this procedure (with soft bags) is that exhaled gas goes into the bag and to a certain degree is returned right back to the patient""s lungs at the following inspiration.
Manual ventilation with soft bags is therefore usually employed with a breathing apparatus generating a constant flow of fresh gas flowing in hoses past the patient. The flow of fresh gas is mixed with the exhaled gas and fills the bag. This reduces re-breathing but is insufficient in many instances.
Periodic replacement of the gas in the manual ventilation bag is one way to reduce re-breathing further, but this causes a brief interruption in the patient""s treatment.
The hard, self-inflating bag does not have this problem. It usually has a valve at each end and is filled through the valve with fresh breathing gas (usually air). Another way is to use coaxial connections, as shown in U.S. Pat. No. 3,291,121. However, as stated above, one common, major disadvantage of all hard bags is the physician""s loss of an ability to feel the lungs. Another disadvantage is the increased number of valves required for the operation of the hard bag. These valves impede flow.
One known way to avoid re-breathing with soft bags is to force expired gas away from the bag during patient exhalation at the same time as fresh breathing gas fills the bag in the exact same way expired gas would have done. In this procedure, the physician is still able to feel the lungs, and only fresh breathing gas fills the bag. This procedure works excellently but requires the use of flow or pressure sensors and relatively rapid control of the valves in the breathing apparatus for evacuating expired gas and admitting fresh breathing gas.
There is a demand and need for a soft manual ventilation bag with the same function as the latter procedure but which is simpler to use in any situation, even when no electricity is available (not even batteries).
An object of the present invention is to provide a soft manual ventilation bag which is simple and easy to use in any situation requiring manual ventilation.
Another object of the invention is to provide a breathing apparatus with a manual ventilation capability.
The first objective is achieved according to the invention in a manual ventilation bag wherein two separate soft bags are combined as to form one manual ventilation bag with two openings allow simple separation of gas flows to and from the patient with no loss of the feeling of the lungs for the operator. The openings to which the soft bags are connected can be arranged side by side, coaxial or in any other suitable arrangement.
When the openings are coaxially arranged, one soft bag is suitably arranged inside the other soft bag. The soft bags can be protected by a soft cover. The soft cover is preferably transparent (as may the other soft bag be in the coaxial arrangement).
The second object is achieved according to the invention in a breathing apparatus having a manual ventilation bag as described above.
The breathing apparatus has several advantages due to the design with two separate soft bags.
The breathing apparatus can be e.g. a ventilator with an inspiratory line and an expiratory line. The inspiratory line is connected to one of the soft bags, and the expiratory line is connected to the other soft bag. To a physician using the manual ventilation bag, inhalations and exhalations will, in principle, feel the same as with a manual single-bag ventilation bag. However, there will be a major difference for the patient, since fresh breathing gas is always supplied for inhalations.